1. Field of the Invention
This invention relates to photothermographic and thermographic elements, compositions and processes for providing a developed image in color. One of its aspects relates to photothermographic elements for providing a developed color image comprising photographic silver halide in association with an oxidation-reduction image-forming combination and certain color-forming couplers. In another of its aspects it relates to photothermographic compositions for providing such a developed image in color containing the described components. A further aspect relates to a thermographic element or composition for producing an image by imagewise heating wherein the element or composition contains the described combination in the absence of a photographic component. A further aspect relates to a process of developing an image in color in an exposed photothermographic element containing the described components by uniformly heating the element.
2. Description of the State of the Art
It is well known to develop a latent image in a photothermographic element using processing with heat. After imagewise exposure, the resulting latent image in the photothermographic element is developed and, in some cases, stabilized, merely by uniformly heating the photothermographic element. Such materials and process are described, for example, in U.S. Pat. No. 3,152,904 of Sorensen et al, issued Oct. 13, 1964; U.S. Pat. No. 3,301,678 of Humphlett et al, issued Jan. 31, 1967; U.S. Pat. No. 3,392,020 of Yutzy et al, issued July 9, 1968; U.S. Pat. No. 3,457,075 of Morgan et al, issued July 22, 1969; British Pat. No. 1,131,108 published Oct. 23, 1968; German Pat. No. 888,045 issued June 29, 1943 and British Pat. No. 1,161,777 published Aug. 20, 1969.
Certain photothermographic materials for producing a developed image in color are also known, as described, for example, in U.S. Pat. No. 3,531,286 of Renfrew, issued Sept. 29, 1970 and U.S. Pat. No. 3,761,270 of deMauriac and Landholm, issued Sept. 25, 1973. The reducing agents employed in the materials of U.S. Pat. No. 3,531,286 of Renfrew are para-phenylenediamines which can be unsuitably toxic. When the paraphenylenediamine is replaced with a less toxic reducing agent such as an amino phenol, no useful color image is developed. In the photothermographic materials of deMauriac and Landholm a base-release agent is needed to provide the necessary color-forming reaction in the photothermographic material. These materials provide increased cost to the photothermographic element and composition. No suitable solution to the elimination of these problems is evident from the described patents.
The described patents of deMauriac et al and Renfrew indicate that a color-forming coupler can be useful in a photothermographic material for producing a color image. However, it is surprising that many color-forming couplers will not provide a useful color image in a photothermographic material comprising certain sulfonamidophenol reducing agents.
Sulfonamidophenol reducing agents have been found useful in photothermographic materials as described, for example, in Belgian Pat. No. 802,519 issued Jan. 18, 1974. It was surprisingly found, however, that certain sulfonamidophenol reducing agents are not acceptable to provide a developed image in color with certain color-forming couplers. This is illustrated in the following comparative examples. While many reducing agents are known in photothermographic materials as described, for example, in U.S. Pat. No. 3,751,249 of Hiller, issued Aug. 7, 1973 and other of the described patents, reducing agents or silver halide developing agents, as a class, do not provide useful color images in photothermographic materials. No suitable solution to the elimination of the described problems is evident from the described patents.
Thermographic materials are also known for providing an image in color. The images in such materials are provided by imagewise heating, not by imagewise exposure to light. Such thermographic materials are described, for example, in U.S. Pat. No. 3,592,650 of DeSelms, issued July 13, 1971 and U.S. Pat. No. 3,094,417 of Workman, issued June 18, 1963. These are not useful for photographic processes in which a latent image is provided by imagewise exposure to light.
Accordingly, there has been a continuing need for improved photothermographic materials that provide a developed image in color employing certain sulfonamidophenol reducing agents and certain color-forming couplers that provide improved photosensitivity, that can provide different colors, such as cyan, magenta, and yellow, and that can avoid the use of undesirable toxic reducing agents, such as para-phenylenediamines. There has also been a continuing need for thermographic materials which are useful for providing an image in color and contain certain sulfonamidophenol reducing agents and certain color-forming couplers.